control of end breaks in warping

Minimising end breaks in warping involves four steps namely:

1. Control of tension in the yarn
2. Satisfactory maintenance of those machines
3. Minimising the defects on packages produced at winding
4. A regular check on the end breakage rate for comparison with the norm.

1. conrol of tension in the yarn

On the warping machine, there are two types of variation in yarn tension
1. Between different stages of unwinding of a package. This can be detected after the first thread guide.
2. Between ends. It can be detected at the head stock.

The tension variation that occurs during the unwinding of a package can be minimised if you design the creel such that the distance between the package and the first thread guide is shortest, it will avoid the yarn balloon rubbing the nose of the package.

The tension variation between the ends at the headstock is minimised if the groups of neighbouring ends on the beam are taken from the same column of packages in the creel.

2. Condition of Machine

a. Alignment of the package at the creel

Non alignment of the creel package with respect to the first guide is often seen to be a cause of high end breakage rate at warping. This alignment is done with the help of a gauge.

b. Eccentric Guide rollers

On machines with mechanical stop motions, there are several guide rollers at the headstock which are positioned very near to one another. Eccentricity in those rollers can introduce short term tension variations of high amplitude.

c. Thread Guides

Deep cuts in thread guides can significantly increase yarn tension and hence deteriorate warping performance. If found dirty, the thread guides should be cleaned with CCl4.

d. Relative humidity and temperature

For satisfactory working at warping, about 60% RH should be maintained. The dry bulb temperature should be kept at about 29 o C (84 o F). Lower humidity may increase yarn hairiness, end breaks and liberation of fluff. The fluff ultimately passes to the beam and given difficulty during sizing. Higher humidity is unnecessary; in fact relative humidity higher than 70% may increase end breakage rate.

Process Control in Warping-3

Process Control in Warping-3

Maintenance Check points at Warping

Machine

1. Clean with compressed air at every creel change-per shift
2. Clean with compressed air and cleaning waste- weekly

Package Alignment at the Creel

1. Look for incorrectly aligned packages, correct if the non-alignment is too severe- regularly
2. completely guage the creel with the help of a gauge- half yearly

Tension Weights

In case of high speed warping machine, check tension weights at every count change- regularly

Tension Level

Check the tension levels with tension meter- Monthly

Stop Motion and Brake

1. Ensure that the machine stops within 1 1/2 revolutions fo the drum in case of high speed warping- regularly
2. Check with condition of drop pins and replace those with cut marks- regularly.

Guide rollers

1. Check for concentricity- half yearly

Beams
1. Check for the conditions of flanges and beam shafts, repair damaged beams- regularly

Creel Fans
1. Check that creel fans oscillate properly and are not chocked with fluff- regularly.

Parts in yarn path

1. Check for cuts in parts of machine in yarns parts regularly.
2. repair/replace the parts with cut marks- weekly

Process control in warping-2

Efficiency of Warping Department

The following will calculate the efficiency of a warping machine:

Let Speed in m/min= 300
Set length (m) = 18000
Yarn length on cone/cheese (m)= 54000
Number of Ends/beam= 500
end breaks/400 ends/ 1000 m = 3
Time to mend a warp break (seconds) = 35
Time to change a beam (seconds) = 500
Time to change a creel (seconds) = 3000
Time loss due to miscellaneous causes/1000 m (seconds)= 25

Calculation

Running time R (s) = 1000x60/300 = 200
R is the uninterrupted running time in meters
Breaks/running ends in beam/1000 m = 3x500/400 = 3.75
Stoppage time /1000 m
(a) to mend breaks (s)= 3.75x35 =131 s
(b) to change a beam (seconds) = 500x1000/18000 = 28 s
(c) to change a creel = 3000x1000/54000 = 56 sec
(d) Miscellaneous time = 25 seconds

Therefore, S, the total stoppage time per 1000 meters (s)= 131+28+56+25 = 240 s

Therefore total efficiency = Rx100/(R+S)= 200x100(200+240) = 45.5 %

Expected Production per shift of 8 hours (m) = (300x60x8x45.5)/100 = 65,500 m

Causes of Low efficiency or Low productivity

1. Increase in End breakage rate

The machine efficiency at warping is highly sensitive to the end breakage rate

2. Improper utilisation of magazine creel

If the creel boy does not keep the magazine creel ready to be used by the time the package in the running creel are over, the efficiency will fall.

3. Reduction in Average Set-length

Lower set lengths reduce the machine efficeincy at warping

4. Number of Tenters per Machine

The number of tenters per machine determine the time to mend an end break. This is because by the time the warper finds a broken end on the beam, the creel boy brings the other end of the broken yarn from the creel

5. Stops due to Machine Breakdown, shortage of cones etc.

If the stops due to machine breakdown, shortage of empty beams or cones/cheeses etc. are high, the actual efficiency of the machine will be lower than calculated.

Process Control in Warping-1

Process Control in Warping

Warping is the process of winding together on a beam a specified number of warp ends from Creel. The creel is a convenient rack for holding spools, cones or cheeses while the yarn is withdrawn to the warp beam.

The following are the process control parameters in a warping department:

1. Minimising End breaks.
2. Quality of warping beam
3. Control of productivity

Importance of Minimising end breaks:

The stoppage of the machine due to an end break is likely to deteriorate the quality of the beam due to three reasons:

1. The rubbing of the beam by the drum which stops abruptly.
2. Owing to the difficulty in finding the broken end, there is a possibility of incorrect mending. It may lead to lappers during sizing.
3. There is some loss in the extensibility of broken end when the machine is stopped, it increases the probability of breakage in weaving and sizing.

The following points should be noted to improve the quality of warping beams:

1. condition of beam flanges:

If the beam flanges are damaged, the unwinding of yarn near the flanges will not be satisfactory. This will cause difficulties in sizing and weaving.

2. Stop Motions and Breaks:

Proper stopping of the warping machine after an end break ensures that the broken end on the beam can be traced easily.

3. condition of the driving drum:

On most warping machines the beam is driven by fricitonal contact with the driving drum. In order to get a package of the correct density, the pressure between the drum and the warper's beam has to be kept at fairly high level.

4. Barrel Diameter of the Beam

Beams of small barrel diameter give rise to high unwinding tension at sizing, particularly when the beam is about to become empty.

5. Cuts in Accessories in the path of yarn

Drop pins of stop motion, guide rollers, reed denting etc. should bot have any grooves.

6. Creel Fans

Fluff accumulated on the machine, particularly at thread guides, causes tension variations in the yarn. This fluff can pass on to the beam.

7. Length Measuring Motion

The length measuring motion should be accurate, otherwise estimation of beam count would be wrong and subsequently will give incorrect values of size percent which is commonly determined from the weights of yarns on the warper's and the size beams.

8. Density of the Beam

The beam should be firm, inadequate pressure between the beam and the drum causes soft beam. Adequate pressure should be maintained by making suitable mechanical adjustments.

Control of Productivity

The productivity at warping depends upon the machine efficiency and machine speeds. The speed is governed by the mechanical condition of the machine and its design. Machine efficiency depends on several factors, such as the breakage rate, the time taken to mend the machine stop, set length, length of yarn on supply package etc.